EP0460586A1

EP0460586A1 - Paintable vehicle sealer patch

Info

Publication number: EP0460586A1
Application number: EP91109067A
Authority: EP
Inventors: Henry W. Griffin; John Johnson; Richard E. Whisler
Original assignee: Essex Specialty Products LLC
Current assignee: Essex Specialty Products LLC
Priority date: 1990-06-08
Filing date: 1991-06-04
Publication date: 1991-12-11
Also published as: ZA914373B

Abstract

A process for assembling a vehicle, applying an electrodeposition coating thereto, and then applying a paint thereto, wherein at least one joint of the vehicle is sealed, characterized in that the joint is sealed prior to the application of the electrodeposition coating, and the sealer patch (1) comprises a metallic sheet (2) with opposed major faces having a layer of adhesive (3) on one side thereof. The process of the invention advantageously provides a vehicle with a patched surface that does not discolor when painted or exposed to heat.

Description

This invention relates to a vehicle sealer patch and, more specifically, to a vehicle sealer patch which is paintable in vehicle assembly processes.
Processes for applying a metal repair patch to an automobile are known and are described, for example, in U.S. Patents Nos. 3,850,718 and 4,473,419. Vehicle repair patches made of corrosion-resistant materials are described in U.S. Patent 4,732,633. Generally, these types of patches are designed for use in repairing damage to the exterior of automobiles and are typically comprised of a layer of material which is coated with a pressure-sensitive adhesive. Such pressure-sensitive adhesives require substantial preparation of the surface of the area to be patched in order for the pressure-sensitive adhesive on the patch to adhere properly.
Paintable patches are used in vehicle assembly processes to seal metal-to-metal joints, and improve their cosmetic appearance. Such patches are comprised of a thin flat piece of an extruded material, such as polyvinyl chloride or an acrylic compound, that is paintable and has just enough surface tack for adhesion on a clean surface. These patches are usually applied just after dip-priming and prior to the subsequent painting of the automobile body. However, such patches require strict formulation in order to be compatible with the chemistry of a particular paint manufacturer, and with the different paint colors of each paint manufacturer. Failure to closely monitor the chemistry of the patch can result in discoloration and/or paint cracking, giving an unacceptable cosmetic appearance. Attempts to continually customize the chemistry of the composition of the patch itself in order to be compatible with each particular paint system are time-consuming and expensive. Another disadvantage of such patches is that they must be applied to a clean surface, in order to adhere throughout the painting process.
Pumpable and extrudable sealants may also be used for sealing such metal-to-metal joints. However, both require a high degree of operator skill to obtain an acceptable cosmetic appearance, especially when used to seal large gaps between pieces of metal. In addition, constant vigil is required to prevent the sealants from getting on surfaces of the automobile which are more visible and require a higher standard of appearance.
This invention is a process for assembling a vehicle, applying an electrodeposition coating thereto, and then applying a paint thereto, wherein at least one joint of the vehicle is sealed, characterized in that the joint is sealed prior to the application of the electrodeposition coating, and the sealer patch comprises a metallic sheet with opposed major faces having a layer of adhesive on one side thereof. The process of the invention advantageously provides a vehicle with a patched surface that does not discolor when painted or exposed to heat. These and other advantages of the invention will be apparent from the following description and drawings which are for illustrative purposes only, and are not intended to limit the scope of the invention.
In the drawings:

Figure 1 - illustrates a sealer patch which has been die-formed;
Figure 2 - illustrates a cross-sectional view of an embodiment of the patch of the invention;
Figure 3 - is a view of an automotive vehicle with a joint which has been sealed by a die-formed sealer patch;
Figure 4 - is a fragmentary portion of Figure 3 showing the patch of Figure 1 in place.

Referring now to Figures 1, 2, and 3 a vehicle sealer patch 1 is shown, which comprises a sheet 2 with a layer of adhesive 3 on one side thereof. Preferably, the adhesive is substantially coextensive with the major face to which it is adhered. Suitable adhesives include, for example, for example, phenolic, epoxy, or rubber-containing adhesive, or blends thereof, urethane adhesives, or acrylic hot melt/polyvinylchloride blends. Preferably, the adhesive of the sealer patch is suitable for bonding to oil-contaminated metal. In addition, the adhesive is also preferably sufficiently electrically conductive to permit an electrodeposition coating to adhere to the patch. The sheet 2 of the patch is comprised of a metallic material which has a paintable surface, such as, for example, aluminum or steel or an alloy thereof, since such materials provide a surface which does not discolor, melt, or crack when painted or heated, and are easily permanently deformable for use on multiple planar or contoured surfaces. The member is most preferably comprised of aluminum, for its flexibility and ease of use in the manufacture of these patches using extrusion or lamination techniques. Preferably, the sheet is substantially rigid but permanently deformable and has a configuration which substantially mates with a joint area to be covered by the patch.
The adhesive 3 of the patch used in the process of the invention preferably comprises an adhesive which is suitable for bonding to oil-contaminated metal surfaces, so that it may be applied before the metal is cleaned. Such types of adhesives include, for example, phenolic, epoxy, or rubber-containing adhesives, or blends thereof, urethane adhesives, or acrylic hot melt/ polyvinylchloride blends. Examples of suitable epoxy and urethane adhesives are described in Bowen, D. O. and C. L. Volkmann, Natl. SAMPE Tech. Conf., 17 (1985), and U.S. Patent 4,842,938. Most preferably, the adhesive is a rubber-containing adhesive. Suitable types of rubber additives and compounding techniques are described in Morton, Maurice, Rubber Technology, 2nd Ed. (1973) and Winspear, George, The Vanderbuilt Rubber Handbook (1968). Examples of types of rubber include, for example, natural rubbers, styrene-butadiene rubbers, butyl rubbers, ethylene-propylene rubbers, synthetic polyisoprenes, polybutadienes, nitrile elastomers, neoprenes, polysulfide rubbers, silicone rubbers, and fluorocarbon rubbers. In the preparation of a rubber-containing adhesive, plasticizers, fillers, solvating fluids, and oils may be employed to aid in the mastication of the rubber starting material.
The adhesive is preferably a thermosetting adhesive, which preferably cures at a temperature at which the electrodeposition layer or paint applied to the vehicle is cured.
Other additives which are preferably employed in the preparation of the adhesive include thixotropes, including fumed silica and clay materials; curing agents, including sulfur, sulfur-bearing chemicals, metal oxides, difunctional compounds, and peroxides; curing agent retarders and accelerators and accelerator activators; tackifying resins, including hydrocarbon resins, talloil resins, phenolic resins, and phenolformaldehyde resins; additional plasticizers; antioxidants and antizonants; and blowing agents.
Additives which provide or enhance the oil-absorbing properties of the adhesives, such as talc or carbon black, are also preferably employed. Since little or no surface preparation is necessary, the patch may be applied during the assembly of the metal components of the vehicle, which are usually oily before the assembled vehicle body is cleaned. The application of such patches early in the assembly process provides for easier installation in places which have limited physical access after the vehicle is assembled.
The adhesive is also preferably paintable, although the adhesive is preferably used in an amount small enough so that a minimal amount of it is exposed around the edges of the patch after the patch is applied. Polyvinyl chloride additives are preferably employed to increase the hardness of the cured adhesive, and curing agents are also preferably employed. The adhesive is preferably a thermoset adhesive which cures at temperatures above about 225°C, which is the average minimum temperature for most vehicle paint ovens. More preferably, the adhesive is a thermoset which cures at temperatures above about 300°F, which is the average temperature at which an electrodeposition coating for a vehicle is cured. The adhesive is also preferably not solvent-based and, if used on a vertical surface, is preferably pressure-sensitive to provide sufficient tack to adhere to the surface. Additives which enhance the ability of the adhesive to provide good contact with the surface to be adhered to are preferably employed and include, for example, oils, plasticizers, tackifiers, hydrocarbon resins, and talloil resins.
The adhesive of the patch is preferably sufficiently electrically conductive to permit an electrodeposition coating to adhere to the patch. This characteristic makes the patch suitable for installation in vehicle assembly processes before the "e-coating" process, wherein the vehicle body assembly is electrodeposited with a material which makes it corrosion-resistant. The suitability of the sealer patch of the invention for use in electrodeposition processes means that the patch may be installed during the body shop assembly of the vehicle, simplifying the installation of such patches in areas which have limited physical access after assembly, such as areas near the trunk lid hinges, or near the hinges on a hatchback. In order for the sealer patch to be suitable for use in e-coating processes, the adhesive must be electrically conductive. One means for increasing the conductivity of the patch is to increase the conductivity of the adhesive. The conductivity of the adhesive may be enhanced with electrically conductive additives such as, for example, carbon black, metal oxides, metal filings, and conductive polymers.
Suitable electrically-conductive adhesives include, for example, phenolic, epoxy, or rubber-containing adhesives, or blends thereof, urethane adhesives, or acrylic hot melt/polyvinylchloride blends, including the examples of these described above. Most preferably, the adhesive is a rubber-containing adhesive. The adhesive is also preferably suitable for bonding to oil-contaminated metal surfaces, so that a minimum amount of, or no preparation of the surface to which the patch is to be applied is necessary. The conductivity of the adhesive may be enhanced with electrically conductive additives such as, for example, calcium carbonate, metal fibers, or carbon black. Preferably, the additive is carbon black which preferably has a large surface area to provide the highest conductivity. The amount of electrically conductive additive needed to provide sufficient electrical conductivity will depend on the thickness of the adhesive, with more additive required with higher thicknesses. When the thickness of the adhesive is about 0.06 inches, the electrically conductive additive is preferably employed in an amount, based on the weight of the adhesive, in the range of from 1.7 percent to 2.5 percent, and is more preferably about 2 percent.
The patch may be applied to seal a joint anytime before the painting process prior to the electrodeposition process, including just prior to electrodeposition or the subsequent curing; prior to or during the cleaning of the assembled body; or anytime during the assembly of the vehicle components. The sealer patch is applied prior to the electrodeposition process so that it may thoroughly cure during the e-coat curing process, and is most preferably applied before the vehicle components are completely assembled, so that the patch may be applied in places which are difficult to physically access after assembly. Advantageously, this patch will not discolor, melt, or crack when painted or exposed to heat during the manufacturing process.
The sheet of the patch used in the process of the invention is comprised of a material which has a paintable surface, such as, for example, aluminum, steel, extruded polyvinyl chloride, and is preferably lightweight and flexible. The sheet is more preferably comprised of a metallic material such as aluminum or steel, since such materials provide a surface which does not discolor, melt, or crack when painted or heated, and are easily permanently deformable for use on multiple planar or contoured surfaces. The sheet is most preferably comprised of aluminum, for its flexibility and ease of use in the manufacture of these patches using extrusion or lamination techniques.
The sealer patch used in the process of the invention preferably has a green peel strength, with respect to the surface to which the patch is applied, such that the sealer patch will withstand phosphating and electrodeposition processes of a vehicle assembly process. This high green peel strength makes the patch suitable for use in manufacturing processes, where such a patch may need to survive phosphating and electrodeposition processes. However, if the adhesive of the patch comprises an oil-absorbant adhesive and is applied to an oily surface, it need not have a particularly high green peel strength immediately upon application because, generally, the longer the time the adhesive has to absorb oil prior to curing, the higher the green peel strength will be. The green peel strength of the sealer patch at the time the vehicle is subjected to such phosphating and electrodeposition processes is preferably at least about 2 psi/inch width, with respect to the surface to which the patch is applied.
The thickness of the sheet of the patch used in the process of the invention is preferably at least about 1.0 mm; and is preferably no greater than about 2.0 mm, and is more preferably about 1.5 mm. These ranges of thicknesses advantageously provide a patch with a thickness which makes it suitable for use as a die-formed part with multiple planar surfaces. The thickness of the adhesive of the patch of the first and second aspects of the invention, as well as the patch used in the process of the invention should be thick enough to cover surface defects and metal imperfection in the vehicle to which the patch is applied, but otherwise be as thin as possible. The thickness of the adhesive is preferably no greater than about 1.5 mm.
The patch used in the process of the invention may be manufactured using an extrusion process, wherein the sheet is coextruded with the adhesive, and then cut into specific shapes and sizes. The patch may also be die-formed to have multiple planar surfaces. The adhesive layer is preferably covered with a release paper following the manufacture of the patch, for ease in shipment and handling. The release paper is preferably applied during the manufacture of the patch and is coextruded with the sheet and adhesive.

Claims

A process for assembling a vehicle, applying an electrodeposition coating thereto, and then applying a paint thereto, wherein at least one joint of the vehicle is sealed, characterized in that the joint is sealed prior to the application of the electrodeposition coating, and the sealer patch comprises a metallic sheet with opposed major faces having a layer of adhesive on one side thereof.
The process of Claim 1 wherein the adhesive is suitable for bonding to oil-contaminated metal.
The process of Claim 1 wherein the patch has a green peel strength of at least about 2 psi/in width.
The process of Claim 1 wherein the sheet comprises aluminum.
The process of Claim 1 wherein the thickness of the sheet of the patch is at least about 1.0 mm.
The process of Claim 1 wherein the thickness of the sheet of the patch is no greater than about 2.0 mm.
The process of Claim 1 wherein the thickness of the adhesive of the patch is at least about 1.5 mm.
The process of Claim 1 wherein the adhesive comprises a rubber-based adhesive.
The process of Claim 1 wherein the adhesive is a thermoset adhesive which cures at temperatures above about 300°F.
The process of Claim 1 wherein the adhesive is sufficiently electrically conductive to permit an electrodeposition coating to adhere to the patch.